JP2004502034A - How to coat super abrasive with metal - Google Patents

Abstract

A method of metal coating diamond superabrasive particles involves heating the superabrasive particles in a common inert atmosphere in the presence of a powder forming a coating of a metal compound. The metal compound contains a metal that can be reduced thermochemically by the superabrasive material acting as a reducing agent. The method forms a chemical bond at the interface between the outer metal layer and the superabrasive particle substrate. The metal-coated superabrasive particles can be separated from powders that are hydrotreated in situ and easily form excess coating by filtration. The product particles are ideal for use in a wide variety of metal bond cutting, machining, dressing and other abrasive tools, especially diamond film inserts and single layer diamond tools.

Description

【００２９】
これらの粉末の存在下で加熱される場合、次の反応によりコーティングがダイヤモンド粒子の表面上に形成される。
ＭｅＯ ＋ Ｃ（ダイヤモンド） ＝ ＭｅＣ ＋ ＣＯ（気体）
ここで、Ｍｅは金属であり、ＭｅＯは金属酸化物であり、且つＭｅＣは金属炭化物である。
【００３０】
本方法の温度は、選択された金属酸化物の初期反応温度に依存する。上記の表に記載されているように、これらの金属酸化物を気化及び化学的に解離させるのに必要とされる反応温度は、約６００〜約１，１００℃の範囲にあり得る。好ましい金属酸化物は、タングステン（Ｗ）、バナジウム（Ｖ）、タンタル（Ｔａ）及びモリブデン（Ｍｏ）並びにそれらの組合わせの酸化物である。これらの金属酸化物とは対照的に、酸化チタン（ＴｉＯ_２）は超研磨材粒子上にＴｉＣの金属コーティングを形成するが、超研磨材は、約１，３００℃のＴｉＯ_２分解温度において望ましくない熱分解を受け得る。約１，１００℃の解離温度を有するＴａ_２Ｏ_５の場合、天然ダイヤモンド粒子は熱損傷を受けることなく基材として用いられ得るが、合成ダイヤモンド粒子は望ましくない熱分解を受ける。従って最高で１，１００℃の気化又は解離温度を有する金属酸化物は、超研磨材粒子をコーティングするための炭素−熱還元法における反応体として用いるために好ましい。酸化タングステンが用いられる場合、約１，０５０℃の温度は、合成又は天然のどちらのダイヤモンドについても好ましい。かかる高温にて形成されたコーティングは、未加熱のコーティングされていないダイヤモンドと比較して、ダイヤモンドの脆砕性の低減をもたらすということが観察された。
【００３１】
加熱過程が続くにつれて、金属コーティングの層は、最初に炭化金属として、そして次いで金属としてダイヤモンド上に堆積する。前記金属は、ダイヤモンド表面の結晶学的方位に依存する速度にてダイヤモンドの露出された表面をコーティングする。有利なことに、本方法は、超研磨材表面上に比較的均一な厚さのコーティングを生じる傾向にある。一般に、暴露が長ければ長いほど、形成される金属層はより厚くなる。金属の堆積は、所望のコーティング厚が達成されたときに、超研磨材とコーティング形成粉末とを隔離することにより、又はコーティング形成粉末を共通の不活性雰囲気から除去することにより止められる。コーティングの堆積を止める他の方法は、混合粒子の温度を下げること及び／又は反応性タングステンの雰囲気をパージするのに有効な高い流速で、反応しつつある粒子上に不活性ガスを通すことである。
【００３２】
不活性雰囲気は、還元及び堆積工程を行うのに関する化学蒸気種を輸送するための媒体を与える。従って、コーティング形成粉末及びコーティングされる超研磨材は共に同じ不活性雰囲気内にあることが重要である。不活性雰囲気は静止状態にあり得るが、いくらかの動きが種を固体材料の方へ移動させ得、またコーティング速度を改善する傾向にある。従って、不活性雰囲気を、固体原料床にわたって通すことが好ましい。流れは、プロセスの間に止められ得る。過度の流れは、蒸気状反応体が超研磨材表面に到達する前に、それらを希釈し且つ運び去り得る。還元反応副生成物、例えば一酸化炭素の濃度は、静止雰囲気中又は再循環雰囲気中で増加し得る。このことは、金属コーティングプロセスを減速させ得る。従って、前記プロセスの間に副生成物の雰囲気をパージすることが望ましい。これは、雰囲気の一部を排出し、且つ排出容量を補充する新鮮な不活性ガスで補充することにより成し遂げられ得る。好ましくは、不活性ガス雰囲気の容量は、１時間当たり約５〜２０回置換されるべきである。
【００３３】
用語「不活性」により、酸素又は還元反応を妨害する他の物質を、不活性雰囲気の組成物が実質的に含まないことが意味される。酸素の不存在は、超研磨材及びコーティング形成粉末上で不活性ガスを掃引するか又は真空を引き起こすことにより達成され得る。真空は、雰囲気中の実質的にすべての酸素の排気を保証するのに有効な圧力にされるべきである。好ましくは、真空は、約３Ｐａ未満の絶対圧の雰囲気を生じるべきである。
【００３４】
周囲圧又はより高い圧力の酸素を含有しない不活性ガスで酸素含有雰囲気を置換することにより、不活性雰囲気を発生させることが好ましい。不活性ガスは、蒸気状反応体を移動させて超研磨材の効率的なコーティングを促進するのに有効な速度で、固体反応体上を通し得る。本発明において用いるのに適した代表的不活性ガスは、アルゴン、ヘリウム、クリプトン、ネオン、窒素、キセノン及びそれらの混合物である。アルゴン及び窒素が好ましい。
【００３５】
上述のように、コーティング形成粉末及び超研磨材粒子は、新しい方法を行うために、相互の物理的接触を必要としない。前記粒子及び前記粉末は、互いに隔離され得る。例えばコーティング形成粉末をるつぼ中に置き、超研磨材粒子を同じ不活性雰囲気内で前記るつぼ上に配置したスクリーン上に置き得る。好ましくは、コーティングは、るつぼ中のコーティング形成粉末及び超研磨材の固体バッチを熱処理に付すことにより回分的に行われる。連続法は、本発明に包含されると想定される。例えばコーティング形成粉末及び超研磨材粒子は、連続的に移動するベルトコンベヤーの機械方向に平行な隣接しているが離れているバンドに連続的に置かれ得る。ベルトは、不活性雰囲気下の炉を通って移動し得る。これらの個々の粒子プロセスの具体的態様は、前記方法の終わりにコーティングされた超研磨材生成物粒子をコーティング形成原料粒子から容易に分離できることを特徴とする。このことは、コーティング形成粒子と超研磨材粒子とがおおよそ同じサイズを有する場合に望ましい。それはまた、ふるい分けのような機械的作業により損傷され得る異なるサイズの生成物粒子を集めることを可能にする。
【００３６】
新しい方法は、コーティング形成粉末と超研磨材粒子の混合物を用いて行われ得る。回分法では、前記混合物は、バッチとして単一るつぼ中に置かれそして次いで熱処理される。
【００３７】
好ましくは、前記混合物は、コーティング形成粉末を超研磨材と乾式混合することにより製造される。前記混合物は、回分的に又は連続的に製造され得る。リボンミキサー、ドラムタンブラー及びＶ形円錐混合機のような慣用の配合装置が用いられ得る。超研磨材粒子を粉砕しないようにするために、低エネルギー配合装置が好ましい。別の好ましい具体的態様において、コーティング形成粉末は、超研磨材粒子のサイズ範囲と異なる範囲のサイズを有する。コーティング形成粉末の粒子サイズは、典型的には、超研磨材粒子より小さい。従って超研磨材粒子は、単に混合物を適切なサイズのふるいを通じてふるい分けすることにより、コーティング形成粉末から容易に分離され得る。生成物粒子を混合物から分離する方法は、好ましくは、水簸法を利用すべきでない。この方法では前記粒子が互いに及びエルトリエーター（「水簸機」）衝撃板に当たって粒子を摩耗させる傾向にあり、それによって粒子サイズを変え及び／又は金属コーティングされた超研磨材生成物を損傷し得る。超研磨材粒子は、混合物を水のような液体に添加することにより、粉末から分離され得る。ここでは、比較的低密度の粉末は浮き、そして比較的高密度の超研磨材は沈む。
【００３８】
別の好ましい観点において、コーティング形成粉末及び超研磨材は、不活性雰囲気に大きい表面積を露出させるように配置するべきである。これは、それらの固体材料を浅い静止床に配置することにより成し遂げられ得る。好ましくは、床深さは、床中の粒子の平均サイズの約２０倍までであるべきである。顆粒状又は他の不規則形状の粒子では、これらの粒子の平均サイズを決定するために用いられる寸法は、それぞれそれらの粒子の通過させない／全てを通過させる最大／最小サイズのスクリーンの公称網目サイズであるべきである。コーティング形成粉末が超研磨材粒子との混合物中にある場合、好ましい床深さは、超研磨材の平均粒子サイズの２０倍までであるべきである。超研磨材がシートの形態にある場合、床深さを決定するために用いられる寸法は、シートの厚さである。従って、約１ｍｍの厚さのダイヤモンドフィルムをコーティングするためには、約２０ｍｍまでの深さの床でコーティング形成粉末を配置することが好ましい。
【００３９】
コーティングを形成する粉末及び超研磨材粒子を熱処理の間に保持する容器は、高温に耐え、且つ本コーティングプロセスを妨害しないようにされた組成を有するべきである。好ましくは、セラミックるつぼが用いられ得る。グラファイトセラミック以外の任意の耐火性セラミック、例えば粘土−グラファイトも、用いるのに適する。
【００４０】
新しい方法を制御するための主要なパラメーターは、温度及び時間である。コーティングを形成する粉末及び超研磨材が不活性雰囲気中で一緒に集成させた後、温度を高めて還元反応を開始させる。一般に、反応が開始する周囲温度よりも高い臨界温度は、超研磨材及び金属化合物の性質に依存する。それは、通常、少なくとも約５００℃である。通常、前記方法はより高い温度においてより速く進行するが、超研磨材の分解温度は越えるべきでない。これは、超研磨材が形態を変えてその超研磨性質、すなわち超硬度を失う温度である。不活性ガス雰囲気において大気圧又はそれ未満の圧力で約１，２００℃を越える温度へのダイヤモンドの暴露は、前記ダイヤモンドを急速にグラファイトに転換させる。好ましい範囲は、最適な反応速度論及び最小の熱損傷のために約７００〜１，１００℃である。
【００４１】
完全な金属コーティングを達成するための経過時間は、超研磨材片のサイズ及びタイプ、不活性ガスの流量、加熱速度並びに反応温度のような因子に依存する。所望の結果をもたらすために、本発明による約５００℃を越える温度での熱処理暴露時間は、少なくとも約３０分、好ましくは少なくとも約１時間、最も好ましくは２〜４時間を必要とする。より長い熱暴露時間が用いられ得る。一般に、不活性ガス下で好ましい温度において、約３００〜８００μｍのサイズのダイヤモンド研磨材粒子の１時間の熱処理につき、約０．１μｍのコーティング厚が達成され得る。本明細書の記載によれば、当業者は、過度の実験なしに、満足な結果を達成するためのプロセス条件の適切な組合わせを同定することができるはずである。
【００４２】
新しい方法の典型的実施において、コーティングされる所望の超研磨材、コーティング用金属及びコーティング形成化合物が選択される。コーティングされる超研磨材片の表面は、金属汚染がないべきである。かかる汚染を除去する慣用方法が利用され得る。超研磨材粒子及びコーティング形成化合物粒子は、不活性雰囲気、好ましくは不活性ガス雰囲気下で、非常に接近して配置される。好ましくは、これらの粒子は、機械的に共にブレンドされて混合物を形成する。その後、温度が上げられる。温度は超研磨材の分解温度未満の高められた値に、超研磨材粒子上にコーティングを生成するのに有効な時間にわたって保持される。コーティングが進行する間、不活性ガスは、原料及び生成物の床を横切って、金属コーティング速度を維持するのに有効な流速にて提供され得る。十分な結合形成が起こったときに、このプロセスを停止し、そして超研磨材粒子を冷却する。コーティングされた超研磨材は、過剰のコーティングを形成する粉末から分離される。これにより、金属外層が超研磨材に化学的に結合されている生成物がもたらされる。
【００４３】
コーティングされた超研磨材粒子の周囲温度への冷却速度は、決定的には重要でない。生成物を熱衝撃冷却することにより生成物を損傷しないことが推奨されるけれども、反応温度から周囲温度への冷却は、１時間未満、好ましくは約３０分未満にて行われ得る。粒子床の温度が約１５０℃未満に下がったときに、不活性ガス雰囲気は除去され得、すなわち酸素含有ガスが導入され得る。次いで、過剰のコーティング形成粉末は、金属コーティングされた超研磨材粒子から分離され、そして回収され、サイズについて分級されそして本発明によるその次のコーティング手順において再び用いられ得る。その後でコーティングされた超研磨材は、外側の金属表面を流れている水素に約６００〜８００℃の温度にて少なくとも約３０分間暴露することによって清浄にされ得る。最後に、生成物は分析され、検査され、そして貯蔵又は輸送のために包装される。
【００４４】
粒子床温度が冷却工程の間に下がりつつあるときに、不活性ガスを水素で少なくとも約３０分間にわたって置換することは、続く別個の酸化物除去清浄工程を省き得るということが見出された。好ましくは、生成物は、温度が約７００〜８００℃の範囲内に保たれている間に、流動水素に暴露される。冷却中のこの水素暴露はコーティング粒子の金属表面を清浄にするのみならず、過剰のコーティング形成粉末のいくらかを、元素状金属又はより低級の酸化物に還元してそれらを生成物からより容易に分離されるようにする。あまりにも多い金属化合物が存在する場合、不完全な清浄がもたらされることになり得る。その場の清浄過程が不完全である場合、金属コーティングされた生成物は変色したように見える。例えばコーティングされたダイヤモンド上の酸化タングステンは、褐色を有し得る。かかる場合、慣用の再度の水素清浄工程が利用され得る。すなわち、コーティングを形成する粉末から単離された生成物を、水素中で再加熱し得る。
【００４５】
新しい方法に従って生成された金属コーティングされた超研磨材粒子は、当該技術において周知の様々な技術により、メタルボンド金属コア研磨工具の研磨部分中に導入され得る。例えば前記粒子は金属結合剤組成物の粒状成分と一緒にされ、圧力下で圧縮（「常温圧縮」）されて造形研磨部分を形成し、次いで焼結され得る。前記粒子はまた、研磨部分を形成させるために熱及び圧力の同時適用を伴う「熱間圧縮」に適する。前記粒子はいわゆる溶浸工具製作法において利用され得る。この方法では、コーティングされた超研磨材粒子は、金型キャビティ中で金属結合剤成分の粉末状マトリックス内に充填され、その後でその間隙を溶融した低融点の溶浸金属又は合金で充たされる。追加的に、コーティングされた超研磨材は、電気メッキ若しくはロウ付け又は場合によってはハンダ付けによる研磨工具への付着に適する（例えば金属工具体又はコアの表面上に研磨材粒の単層で）。
【００４６】
コーティングされた超研磨材の使用は、ダイヤモンド／金属結合剤の接着、並びに切断砥石、ダイヤモンド鋸刃及びドリルビット、単層研磨材メタルボンド工具、研削砥石、機械加工工具、ドレッシング工具並びにコーティングされた研磨工具及びベルトの研磨材及び工具の寿命を有利に改善する。更に、コーティングされた超研磨材は、不活性雰囲気を必要とすることなく酸素の存在下での、ある種の研磨工具部品の製造を可能にする改善された耐酸化性を有する。
【００４７】
本発明のコーティングされた超研磨材の特定の利点が、工具コア又は体に研磨要素をロウ付けする際に観察された。過去において、いくつかの工具は、超研磨材への熱損傷を避けるために、非酸化性雰囲気下で工具コア又は基材（例えばシャンク、シリンダー、ホイールコア又はディスク）の金属に、研磨又は切削要素をロウ付けすることにより作られねばならなかった。非酸化性雰囲気の使用はコストがかかり、また製造プロセスの複雑さを高める。超研磨材表面上に金属コーティングを付与することにより、ロウ付け作業は大気条件下で行われ得、またより高温のロウ材が用いられ得る。より高温のロウ材は工具体と研磨又は切削要素との間のより耐久性の接着層をもたらし得、従って更なる利点が、工具のより長い寿命において実現され得る。
【００４８】
実施例
さて、本発明はその或る代表的な具体的態様の例により例示される。ここで、これらの例において部、割合及び百分率はすべて、別段指摘されていなければ重量による。当初はＳＩ単位で得られていない全ての、重量及び尺度の単位を、ＳＩ単位に換算した。顆粒の粒子サイズ測定は「ｘ／ｙメッシュ」呼称規約を用いており、ｘ及びｙは米国ふるい系列のふるい呼称番号であり、ｘは粒子のすべてが通過する最小網目に相当し、またｙは粒子のいずれもが通過しない最大網目に相当する。すなわち、４０／５０メッシュダイヤモンドは、４２０μｍの目のメッシュを通過し、また２９７μｍの目のメッシュにより保持される。
【００４９】
実施例１
５０ｇの４０／５０メッシュＤｅ Ｂｅｅｒｓ銘柄ＳＤＡ１００＋合成ダイヤモンドを、７５ｇの−４００メッシュ（すなわち、３７μｍのふるい目を通過する粒子）酸化タングステン（ＷＯ_３）粒子を保持するセラミックるつぼ中に入れた。これらのダイヤモンドと酸化タングステンをスパチュラを用いて手で撹拌して、自由流れ均一混合物を得た。前記るつぼをＬｉｎｄｂｅｒｇレトルト炉中に置き、そして前記炉を窒素で１４２Ｌ／ｈ（１時間当たり５立方フィート「ＣＦＨ」）にて連続的に掃引して排気した。炉温を、１分当たりおおよそ１０℃にて１，０５０℃に上げた。２５０℃に達したときに、アルゴンを窒素の代わりに、同じ速度にて前記レトルトを通じて掃引した。ダイヤモンド／酸化タングステン混合物を、このアルゴン雰囲気中で１，０５０℃で３０分間にわたって保持した。次いで、加熱ジャケットを前記レトルトから引き離して、前記炉を約１０分で７５０℃に冷却した。この温度において、水素をアルゴンの代わりに、同じ速度で前記レトルトを通じて掃引した。前記加熱ジャケットを前記レトルト炉の近くに戻し、そして制御装置を、アルゴン下で３０分間にわたって炉温を７５０℃に維持するよう設定した。その後、前記加熱ジャケットを再び前記レトルト炉から取り去って、前記炉を約２０分かけて室温に冷却した。前記レトルト炉への水素流れを、温度が１００℃に下がったときに止めた。この混合物を１００メッシュふるいに通すことにより、ダイヤモンドを回収した。目視検査により、これらのダイヤモンドが光沢のない灰色の表面色を有していることが分かった。Ｘ線回折分析により確認されていたような、タングステンで予めコーティングされたダイヤモンドは、同様な色を示していた。従って、この例のダイヤモンドはタングステン金属で満足にコーティングされたということが結論付けられた。また、Ｘ線回折により金属層中の炭化タングステンの存在が示され、オージェ分析によりコーティング中の炭素及びタングステンの存在が確認された。
【００５０】
実施例２
７．６８ｇの３０／４０メッシュＤｅ Ｂｅｅｒｓ銘柄ＳＤＢ１１２５合成ダイヤモンドを１１．５２ｇの酸化タングステンと混合したこと以外は、実施例１の手順を繰り返した。ダイヤモンドを酸化タングステンから分離した後、目視検査により、コーティングされたダイヤモンドの表面がまだらな褐色／灰色の色を有していることが分かった。この表面特性は、タングステンが酸化されているタングステンコーティングされたダイヤモンドで典型的である。
【００５１】
これらの酸化タングステンでコーティングされたダイヤモンドをきれいなるつぼ中に入れ、そしてこれを炉中に入れた。炉を前の例のように窒素で掃引し、そして温度を７５０℃に上げた。２５０℃に達したときに、窒素を、同じ流量の水素掃引により置換した。コーティングされたダイヤモンドを、この水素中で７５０℃に３０分間にわたって保持した。その後、加熱ジャケットをレトルト炉から離して炉を室温に冷却し、そして水素流れを止めた。目視検査により、これらのコーティングされたダイヤモンドの表面色が光沢のない灰色であることが示され、またこれらのダイヤモンド上のタングステンコーティングが満足なものであることが示された。これらのコーティングされたダイヤモンドは、コーティング後に７．９２ｇの重さがあり、０．２４ｇの総重量増加を示した。
【００５２】
実施例３
１．０３ｇの天然ダイヤモンドを１．５４ｇの酸化タングステンを用いてコーティングしたこと以外は、実施例１の手順を繰り返した。操作条件もまた、コーティングを達成するために炉を１，０００℃まで加熱し、そして４時間にわたって保持したこと以外は同じであった。また、水素流れは、炉が室温に冷却されたときに止めた。酸化タングステン粒子からの分離の後で、コーティングされたダイヤモンドは、光沢のない灰色の表面色及び１．０４１４ｇの総重量を有していた。従って、これらのダイヤモンドは、合計で０．３７３７ｇのタングステン金属コーティングを得た。同様な方法により前もってコーティングされたダイヤモンドのオージェ深さプロフィル分析により、タングステンコーティング厚はおおよそ０．４μｍであったことが示唆される。
【００５３】
実施例４
４０．０１１７ｇの３０／４０メッシュ天然ダイヤモンドを６０．０１７６ｇの酸化タングステンを用いてコーティングしたこと以外は、実施例２の手順を繰り返した。２度目の水素熱処理後、ダイヤモンドは光沢のない灰色の表面色を有していた。これはタングステンでの満足なコーティングが得られたことを示している。
【００５４】
実施例５
ダイヤモンドフィルム（マサチューセッツ州ウースターのＮｏｒｔｏｎ Ｃｏｍｐａｎｙ）の２５．４ｍｍ×２５．４ｍｍの正方形状でおおよそ０．５ｍｍの厚さの２つの試料は、当初それぞれ０．９４２８ｇ及び０．８９５ｇの重さがあった。各フィルムは、粗いテクスチャード加工されて艶消仕上げされた片面及び滑らかな光沢反対面を有していた。各フィルム試料の光沢面を、Ｎｉｃｒｏｂｒａｚ（登録商標）Ｇｒｅｅｎ Ｓｔｏｐ−Ｏｆｆ（登録商標）タイプＩＩペイント（ミシガン州マディソンハイツのＷａｌｌ Ｃｏｌｍｏｎｏｙ Ｃｏｒｐ．）で塗装した。これは、懸濁されたセラミック粉末のラテックスであると考えられる。前記ペイントを乾燥し、それによって前記フィルムの光沢面をマスクした。初期ダイヤモンドフィルム重量の１．５倍の重さのある４００／メッシュ酸化タングステンの床上で、塗装面を下にして、各フィルムをセラミックるつぼ中に置いた。次いで、これらのフィルム試料の粗い面を、実施例２の手順に従ってタングステンでコーティングした。
【００５５】
２度目の水素熱処理後、目視検査により、これらのダイヤモンドフィルムが粗い面において光沢のない灰色の色を有していることが分かった。これは満足なタングステンコーティングが得られたことを示す。これらのフィルムの光沢のある面に関して、マスキング材はなくなっていた。わずかなタングステンコーティングが縁近くで明白であったが、中央域においてはコーティングは見られなかった。コーティング後、フィルム試料は０．９８５２ｇ及び０．９０６１ｇの重さがあった。これはそれぞれ、０．０１５４ｇ及び０．０１１１ｇの重量増加を示している。
【００５６】
実施例６
酸化タングステン粒子床をるつぼ中に配置し、鋼スクリーンを前記床の上に設置した。その金属スクリーン上に、天然ダイヤモンドを、前記酸化タングステン粒子のいずれにも接触しないようにして置いた。前記るつぼの内容物をアルゴン中で１，０００℃に加熱し、４時間保持し、そしてそれ以外の点では実施例５でのように処理した。終わりに、生成物の検査により、ダイヤモンド表面は光沢のある灰色の金属の連続的な断片状部分で部分的にコーティングされていることが分かった。前記金属は前記ダイヤモンドを完全にはコーティングしなかったけれども、ロウ付けがその部分的にコーティングされたダイヤモンドと研削工具の金属基材との間の強い金属結合を作るのを可能にするのに十分な量の表面が覆われた。
【００５７】
実施例７
５．１５６９ｇの総量の４０／５０メッシュＤｅ Ｂｅｅｒｓ銘柄ＳＤＢ１１２５ダイヤモンド及び７．７３５４ｇの−４００メッシュ酸化タングステン粉末を、セラミックるつぼ中に入れた。これらのダイヤモンドと酸化タングステンをスパチュラで混合して、さらさらした（自由流れ）均一混合物を得た。前記るつぼを真空炉（ニューハンプシャー州エプソムのＯｘｙ−Ｇｏｎ Ｉｎｄｕｓｔｒｉｅｓ， Ｉｎｃ．）中に置き、そして炉温を１，０５０℃に上げるよう温度制御装置を設定した。前記炉をメカニカル真空ポンプで、約３Ｐａ（０．０３ｍｂａｒ）の絶対圧に真空排気した。ダイヤモンド／酸化タングステン混合物を真空下で１，０５０℃に６０分間保持し、その後で炉温を室温（３８℃）に冷却するよう炉温制御装置を設定した。１分当たり約１０℃にて温度を下げる自動冷却ファンにより吹き込まれる冷却用空気を入れる内部シャッターを、前記炉は備えていた。混合物を１００メッシュスクリーン上に注いで、ダイヤモンドを酸化タングステンから分離した。
【００５８】
これらのダイヤモンドは、重度に酸化されたタングステンコーティングの典型である紫色の色を示した。それらを清浄化なるつぼ中に入れ、そしてこのるつぼをＬｉｎｄｂｅｒｇレトルト炉中に置いた。この炉を１４２Ｌ／ｈにて水素ガスで掃引し、そして温度を７５０℃に上げた。これらのダイヤモンドを、水素雰囲気中で３０分間にわたって７５０℃に保持した。次いで、炉温制御装置を止め、そして加熱ジャケットを前記レトルト炉から引き離した。炉温が１００℃に下がった後、水素ガス流れを止めた。ダイヤモンドは光沢のない灰色の表面色を有しており、これは満足な酸化されていないタングステンコーティングの存在を示している。引き続いて、これらの金属コーティングされたダイヤモンドは、０．５６３７ｇの重量増加に相当する５．７２０６ｇの重さがあることが分かった。
【００５９】
実施例８
ダイヤモンド結晶の脆砕性に対する反応温度の影響を決定し、また本発明のコーティング方法が工具製造のために必要とされる強靱なコーティングをされた研磨材粒を生じるかどうかを確定するために、調査を行った。
【００６０】
ダイヤモンド研磨材粒（Ａｍｅｒｉｃａｎ Ｂｏａｒｔｓ Ｃｒｕｓｈｉｎｇ，天然のブロック状ダイヤモンド、２５／３０メッシュサイズ）を、ウィスコンシン州ミルウォーキーのＣｅｒａｃ Ｉｎｃ．により供給されるＷＯ_３粉末と混合し（５ｇのダイヤモンド及び７．５ｇのＷＯ_３）、そして下記に列挙された温度及び時間で加熱した。下記の表に列挙された変数以外は、反応は実施例４に記載されたように行った。
【００６１】
コーティングされた粒を残存する酸化タングステン粉末から分離した後、ダイヤモンド粒の脆砕性をＦＥＰＡ（Ｆｅｄｅｒａｔｉｏｎ Ｅｕｒｏｐｅｅｎｎｅ Ｄｅｓ Ｆａｂｒｉｃａｎｔｓ Ｄｅ Ｐｒｏｄｕｉｔｓ Ａｂｒａｓｉｆｓ）の鋸用ダイヤモンドグリットの相対強度を測定するための標準規格（ＦＥＰＡ Ｓｔａｎｄａｒｄ ｆｏｒ Ｍｅａｓｕｒｉｎｇ ｔｈｅ Ｒｅｌａｔｉｖｅ Ｓｔｒｅｎｔｈｓ ｏｆ Ｓａｗ Ｄａｉｍｏｎｄ Ｇｒｉｔｓ，第１版，１９９４年５月３０日）の改変により測定した。
【００６２】
ＦＥＰＡダイヤモンド脆砕性試験標準規格の改変は、（１）試験球としてのグレード２５ ５２１００鋼玉軸受けを用いること、（２）ダイヤモンド試料を０．４０００±０．０００５ｇに量り取ること、（３）いくつかのふるいサイズを代用すること（特に、上方制御ふるいサイズ９１５を９２０により、また６４５を６５０μｍにより、下方制御ふるいサイズ６００を６０５により、５０５を５０９により、また４２５を４２９により、並びに破壊ふるいサイズ６００を６０５により、５０５を５０９により、また４２５を４２９μｍにより置き換えた）、（４）振動ふるいを、ふるい振とう機の代わりに用いること、及び（５）結果は、ダイヤモンド粒の半減期に達するのに必要とされるサイクル数として記録し、また報告すること（ＦＥＰＡ標準規格は、ダイヤモンドの半分を破壊するのに必要とされる時間を用いる）から成っていた。ダイヤモンドのコーティング特性の脆砕性結果及び目視観察が、下記の表に列挙されている。
【００６３】
【表２】

【００６４】
これらのデータは、８００又は８５０℃の温度にてタングステンでコーティングされた粒（試料２〜４）と比較して、１，０５０℃の温度にてタングステンでコーティングされた粒（試料６）での、ダイヤモンド研磨材粒の靱性の予期されない増大（すなわち比較的小さい脆砕性）を示している。改善はまた、コーティングなしの粒（試料１及び５）と比較して観察された。この実験について選ばれたプロセス条件下で、コーティングは、反応が比較的高い温度にて行われた場合に連続的であり、また反応が比較的低い温度にて行われた場合断続的であった。これらの結果は、連続コーティングの利点を示唆している。タングステンの熱膨張係数はダイヤモンドの熱膨張係数より約４９％大きいので、コーティングされたダイヤモンドの改良された靱性は、冷却中の連続タングステンコーティングの収縮（それによってダイヤモンドを圧縮状態に置く）からもたらされ得る。
【００６５】
本発明の特定の形態は説明のために選択されており、以上の記載は本発明のこれらの形態を当業者に対して十分に且つ豊富に記載する目的のために特定の用語で作成されているが、実質的に同等の又は優れた結果及び／又は性能をもたらす様々な置換及び改変は請求項の範囲及び精神内にあると考えられるということが理解されるべきである。[0001]
The present invention relates to a method for coating superabrasive particles with a metal. More particularly, the present invention relates to a method of producing a diamond abrasive piece coated with a thin layer of metal, wherein the thin layer is chemically bonded to the underlying abrasive. . The coated pieces here are particularly useful for making metal bonded superabrasive grinding and cutting tools, or metallized diamond articles.
[0002]
Diamond superabrasives have the highest hardness that allows other extremely hard materials to be polished. For example, superabrasive tools are often used to shape, dress or sharpen other abrasive tools. Therefore, grinding and cutting tools that utilize abrasive portions that include superabrasives are very important in the industry.
[0003]
In a simplified sense, a superabrasive tool is basically a superabrasive piece, a metal core for tool quality structure, and a single layer of superabrasive material attached to the core in a composite structure or to the core. As a metal binder. The pieces may be irregular particles, sometimes referred to as grit, granules or granules, or they may be precisely shaped articles such as diamond films and shaped polycrystalline composites. Shaped diamond inserts are also used to machine hard abrasive materials such as metal matrix composites and cast aluminum alloys. A so-called single layer particle tool is defined as an abrasive layer bonded to a core, said layer thickness being the nominal thickness of only a single abrasive piece.
[0004]
There are a number of ways to make metal bond superabrasive tools. Many methods, such as brazing or soldering, place the granules on a core in contact with the binder composition, heat these assemblies until the binder composition liquefies, and then cool and combine And solidifying the agent composition. Ideally, the metal binder composition will adhere firmly to the core metal and adhere the granules to the core. A major drawback of this method is that many preferred metal binder compositions are not strongly adherent to superabrasives. Poor adhesion results in inadequate bond strength, which results in premature loss of abrasive particles from the tool during operation. This is particularly problematic for single layer particle tools where it is desirable to have as little binder around the granules as possible to expose the maximum cutting surface. If the adhesive thickness is increased to improve the adhesion, the abrasive granules will be buried deeper in the adhesive, whereby less cutting surface will face the workpiece. In addition, the thick adhesive layer wears out during use, leaving an unsuitable amount of low-strength adhesive layer to hold the granules, whereby the granules are easily released from the tool.
[0005]
A well-known method for increasing the adhesion of a superabrasive to a metal binder is to utilize a binder composition that is reactive to the superabrasive to provide a binder composition during tool fabrication. Is to adhere to the surface of the abrasive particles. However, many powdered metal binder compositions for superabrasive bonding are classified as non-reactive. This is because they do not chemically bond with the superabrasive. Lack of chemical bonding to the superabrasive results in premature release of the superabrasive.
[0006]
A better adhesion improving technique involves introducing a reactive metal component into the precursor binder composition. This component is characterized by its ability to react directly with the superabrasive to form a strong chemical bond between the metal part and the granules. Thus, these so-called "active metal" binder compositions have both non-reactive and reactive components. Usually, the non-reactive components make up most of the binder composition. The non-reactive components alloy to form a strong, durable binder that is adhesive to the core. The reactive components adhere strongly to the superabrasive by chemical bonding and are tacky to non-reactive alloys. For example, U.S. Pat. No. 4,968,326 to Wand discloses a method of making a diamond cutting and polishing tool. The method comprises mixing a carbide-forming substance with a brazing alloy and a temporary binder, applying the mixture to a tool substrate, applying diamond particles on a tool coated with the mixture, and thus combining together. Heating the reduced material to first form a carbide coating on the diamond. The carbide-coated diamond is then brazed to the tool.
[0007]
Despite improvements over the prior art, active metal technology has the added advantage of ensuring that the reactive metal component is present on the surface of the superabrasive granules where the reactive metal component is desired to form a chemical bond. Present a problem. In a basic aspect of this technology, the reactive metal component is mixed in particulate form with other components of the metal binder composition. This mixture is then applied either as a paste or in a dry state. Only that portion of the reactive metal component that is proximate to the superabrasive is directly associated with the abrasive. Reactive metal components elsewhere in the binder composition are redundant or, at worst, detrimental to the overall binder properties. Therefore, in order to provide the reactive metal component with the finest possible particle size and to obtain intimate contact between the superabrasive and the reactive metal component during binder formation, the reactive metal component is It is important that they are evenly incorporated into the mixture.
[0008]
One proposed approach to solving this problem is to coat the superabrasive granules with a reactive metal component prior to mixing with the other binder components. This ensures that the reactive metal component is optimally positioned at the right time for the formation of the binder. For example, U.S. Pat. No. 5,855,314 to Shiue et al. Teaches a coating method in which reactive metal component particles are mechanically bonded to the surface of the superabrasive particles. This involves mixing the reactive metal component powder with a liquid binder to form an adhesive paste, mixing the paste with abrasive particles to wet the particles, and drying the mixture to dry the active ingredient into the particles. Achieved by attaching. Nevertheless, in order to achieve a uniform coating of the particles, it is important that the particle size of the reactive metal component particles be as small as possible. Even when supplied as a fine powder, the reactive metal component is present at a high molecular weight and is therefore usually present on the surface in excess of the amount required to adhere the binder to the superabrasive. Because reactive metal components and superabrasives are often irregularly shaped particles, it is difficult to ensure that the coating is complete or uniform over the entire surface of the superabrasive.
[0009]
Other methods of applying a very thin layer of metal on a substrate are known. These include physical vapor deposition (PVD) and chemical vapor deposition (CVD). The former involves injecting electrical or thermal energy to miniaturize a metal target and condensing the resulting hot metal atoms on a relatively cold substrate. This procedure does not form a chemical bond between the deposited metal and the substrate. CVD methods introduce a metal compound in gaseous form into a heated CVD chamber having a substrate to be coated. Heat decomposes the gaseous metal compound (eg, tungsten hexafluoride) to provide metal atoms that coat the substrate and remove gaseous dissociation by-products, which are typically gaseous.
[0010]
Sometimes, CVD can create a chemical bond between the metal and the substrate, rather than merely mechanically coating the substrate with the metal. This is a very attractive attribute. Because it allows abrasive tool manufacturers to glue this superabrasive with a pre-bonded metal coating to the tool core using simple flux brazing or induction furnace methods in air. Because you do. If the metal coating is not previously chemically bonded to the superabrasive, the tool must be manufactured in a much more complicated and costly way, such as by brazing in an inert gas or vacuum controlled atmosphere. .
[0011]
Unfortunately, CVD results in the formation of a bond between the metal and the substrate only in some metal / superabrasive systems, and only in extreme heat applications. Also, gaseous by-products can be harmful to the substrate. This phenomenon is discussed by Chen et al. In U.S. Pat. No. 5,224,969 relating to a method of coating chromium-coated diamond particles with tungsten by CVD. This patent describes that CVD utilizing tungsten hexafluoride emits a fluorine-containing gas that reacts detrimentally with chromium. Thus, Chen et al teach a suitable, but complex, three-layer coating method using CVD to apply the third layer. Further, gaseous reactants and by-products associated with CVD coating methods are highly toxic to humans.
[0012]
It would be highly desirable to produce superabrasives having ultra-thin coatings of reactive or non-reactive metals without the difficulties and disadvantages associated with the above methods. Further, it is desirable to easily produce a coating of a reactive metal directly on the surface of a superabrasive without the need for an intervening barrier metal layer. There is also a need for a fast method of making chemically bonded metal coatings on superabrasives. This is a metallized coating suitable for making long lasting and effective abrasive or cutting tool inserts that can be attached to the tool holder using conventional methods such as flux / brazing in air or induction furnace heating. To provide a source of superabrasive material. Such tools are characterized by a metal bond between the superabrasive and the core which exhibits exceptional strength, low binder content and very high abrasive particle exposure to the workpiece. Still further, it is desirable to generate a reactive metal coating on the superabrasive particles to cover the superabrasive uniformly over the entire surface of the substrate.
[0013]
Accordingly, the present invention provides a method for coating a superabrasive with a metal. The method comprises heating the superabrasive, and a powder forming a coating comprising a metal compound that is thermally reducible by the superabrasive, to a temperature greater than ambient temperature in an inert atmosphere; A continuous metal layer that maintains the superabrasive at a temperature above the ambient temperature for a duration effective to reduce the metal, thereby chemically bonding at least a portion of the surface of the superabrasive. Forming a metallized superabrasive having the formula: and separating the powder forming the coating from the metallized superabrasive.
[0014]
This new method utilizes solid state coating precursors, heating to extreme temperatures, feeding and handling gaseous metal compounds in CVD reactors, or product units such as conventional PVD or CVD. There is no need to inject large amounts of energy per mass. The method makes it possible to coat the metal uniformly over the superabrasive. Advantageously, the coating thickness can be controlled on a molecular scale so that there is only the desired amount of coating metal to enhance the adhesion between the binder and the superabrasive. The new method of metal-coated superabrasive products is suitable for the production of grinding, cutting and machining tools of all types of bonded and coated superabrasives, especially for metal bond single-layer superabrasive tools, and for metal matrix Ideal for bonded superabrasive cutting, grinding and dressing tools.
[0015]
The term "particle" is used herein to mean any generic solid individual object and does not refer to a particular size or shape. As applied to superabrasives, the term "particle" is intended to refer to a piece of superabrasive having an irregular or predetermined shape. Irregular shaped superabrasives are sometimes referred to as grains, grit or granules. Typical examples of shaped structures include spheres, cubes or other polyhedra, and sheets or films. "Sheet" or "film" is defined by three orthogonal characteristic dimensions, where two of these dimensions mean a substantially flat, generally flat geometric object with respect to a third dimension. . The term "powder" is used herein to mean an individual piece of material that forms a solid coating, regardless of size and shape. With respect to the material forming the coating, "powder" may mean either a single individual solid piece or a plurality of such pieces. Unless otherwise indicated, the size and shape of the superabrasive particles can be the same or different than the powder of the metal compound forming the coating.
[0016]
In a basic aspect, the present invention relates firstly to forming an elemental metal coating on superabrasive particles. The metal coated on the superabrasive particles is provided as a component of the compound in powder form. The coating is performed using a basic inorganic chemical reduction reaction performed at an elevated temperature in an inert atmosphere. The superabrasive acts as a reducing agent that reacts with the elemental metal from the metal compound, whereby the metal forms a chemically bonded coating on the surface of the superabrasive particles.
[0017]
The method advantageously utilizes a chemical reaction between the coating metal and the superabrasive to form a strong chemical bond at the interface between the metal and the superabrasive. With exposure to high temperatures, the new method produces a structure that includes a superabrasive substrate and a layer of metal that is bonded to the substrate by chemical bonding. Here, the layer forms an intermediate layer between the superabrasive substrate and the outer metal layer. This results in a stronger adhesion between the metal and the superabrasive than the mechanical coating normally available.
[0018]
It is a feature of the new process that the source of the metal forming the coating is a powdered metal compound that can be thermochemically reduced to elemental metal by a reducing agent. Further, the superabrasive itself is preferably the only reducing agent present to accomplish the thermochemical reduction. That is, the reduction step of the method can be performed in an environment substantially free of other reducing agents. By "substantially free" is meant that the other reducing agent is not present in an amount that appreciably interferes with the superabrasive coating, and that the absolute absence of any other reducing agent Is not interpreted to mean. That is, a small portion of the surface of the superabrasive particles is consumed in the step of reducing the metal compound. Fortunately, a very thin layer of metal on the superabrasive is sufficient and negligible of the superabrasive to obtain a metal-coated superabrasive grain suitable for strong metal bonding to the abrasive tool Only the amount should be consumed for reduction purposes.
[0019]
Synthetic, natural and CVD diamond and polycrystalline diamond (PCD), and mixtures thereof, are suitable for use in new methods. The size of the superabrasive grains conventionally used in abrasive tools works well in the new method. Such particles are typically irregularly shaped and preferably have characteristic dimensions in the range of about 0.1 μm to 5 mm. A much narrower particle size range can be used in any given abrasive tool application. The particle size of typical commercial superabrasive grains typically ranges from about 0.0018 inches (0.045 mm) to about 0.046 inches (1.17 mm). The particle size of certain superabrasive grains, sometimes referred to as "microabrasives", can range from about 0.1 μm to about 60 μm. The size of the abrasive grains is usually determined by sieving the grains through a sieve having precisely sized holes. Thus, the term "characteristic dimension" refers to the nominal pore size of the sieve through which the particles pass or do not pass.
[0020]
The new method is also suitable for metallizing superabrasive objects larger than about 5 mm. These objects may be irregularly shaped, granular large crystals, or objects of predetermined shape, such as thin sheets or objects of more complex structural shapes (eg, cones, rods, bars, disks, etc.). Thin superabrasive sheets include rectangular diamond sheets preferably having a length and width of about 5-250 mm and a thickness of preferably about 0.2-2 mm, more preferably about 0.5-1 mm. . Such sheets can be made by CVD and are often referred to as "diamond films". The new method is easily adapted to coat large pieces of superabrasive by placing the superabrasive on or within a bed of powder of the metal compound forming the coating.
[0021]
Usually, the entire surface, including both sides, of the abrasive particles in sheet form is coated. Optionally, large particles can be masked to achieve a predetermined surface coating pattern. This optional mask technique prevents the metal from coating part of the surface. Thus, for example, masking can achieve selective coating of only one side, only the edges, all but the edges, and a portion of each side of the superabrasive particles in sheet form.
[0022]
The superabrasive particles can be masked by applying a layer of a barrier material to the surface before starting the heat treatment step of the method. The mask may be removed during or after coating is complete, resulting in superabrasive particles in which the unmasked portions of the surface are coated with metal and the masked surface portions are uncoated. Suitable barrier materials include refractory oxides, nitrides, carbides, ie, compounds that are more stable than the metal-containing compound. Examples of barrier materials include carbides of alumina, yttria, zirconium and titanium.
[0023]
The metal compound should be a metal compound that forms a preselected coating that can be thermochemically reduced by the superabrasive to form the metal in elemental form. Preferably, the metal is firstly selected to achieve the desired purpose of the particular coating application. For example, especially in the manufacture of metal bond polishing tools, it is particularly desirable to provide a coating-forming metal that is compatible with the metal binder composition and reactive with the superabrasive. Metal binder compositions for abrasive tools are well known in the art. Representative metal components in a typical metal binder composition are tin, copper, silver, nickel, zinc, aluminum, iron, cobalt and mixtures thereof. Tungsten is a particularly preferred coating forming metal. Preferably, the metal compound is an oxide of the metal that forms the preselected coating, with tungsten oxide being much more preferred.
[0024]
The amount of raw material present should be sufficient to provide the desired thickness of the metal coating on the superabrasive. That is, the total amount of metal should be greater than the stoichiometric amount required to produce the desired thickness of the metal coating. The superabrasive particles used in a metal bond single layer polishing tool should be well coated when the metal layer is at least about 2 molecules thick. Usually, measuring such small dimensions is not practical. For purposes of defining the present invention, an average metal coating thickness of at least about 100 nm is considered appropriate. Generally, the total weight of the coating-forming powder depends on the surface area of the superabrasive to be coated. Relatively small abrasive particles may require more coating forming powder per unit weight than relatively large abrasive particles. This is due to the relatively small particles having relatively large surface area to mass values.
[0025]
In a preferred embodiment of the present invention, the diamond can be coated with tungsten by heating the diamond and tungsten oxide coating forming powder together in an inert atmosphere. Tungsten oxide is provided as a bright yellow powder, and diamond is present in granular or shaped particle form. If the coating forming powder and the superabrasive particles are present in a common oxygen-free atmosphere, and preferably are in close proximity to each other, the superabrasive and the coating forming powder may be in physical contact with each other. If not, a chemically bonded coating is formed.
[0026]
Without wishing to be bound by any particular theory, it is believed that the tungsten carbide bonded coating of tungsten on diamond is formed according to the following chemical reactions [I] and [II].
WO ₃ + 3C → W + 3CO [I]
W + C → WC [II]
Unexpected phenomena of this coating without the raw solids touching each other can occur. This is due to the fact that some of the tungsten oxide vaporizes and chemically dissociates to form a tungsten coating at an acceptable rate. Tungsten is carbonized on the surface of the diamond to form tungsten carbide. The reduction reaction also forms carbon monoxide gas. This gas is purged from the atmosphere as described below.
[0027]
Other metal oxides may be used in place of or in combination with tungsten oxide in the superabrasive coated carbon-thermal reduction method of the present invention. Suitable metal oxides as well as initial reaction temperatures for each metal oxide are listed in the table below.
[0028]
[Table 1]

[0029]
When heated in the presence of these powders, the following reaction forms a coating on the surface of the diamond particles.
MeO + C (diamond) = MeC + CO (gas)
Here, Me is a metal, MeO is a metal oxide, and MeC is a metal carbide.
[0030]
The temperature of the method depends on the initial reaction temperature of the selected metal oxide. As described in the table above, the reaction temperatures required to vaporize and chemically dissociate these metal oxides can range from about 600 to about 1,100 ° C. Preferred metal oxides are oxides of tungsten (W), vanadium (V), tantalum (Ta) and molybdenum (Mo) and combinations thereof. In contrast to these metal oxides, titanium oxide (TiO 2) ₂ ) Forms a metal coating of TiC on the superabrasive particles, but the superabrasive is TiO.sub. ₂ At the decomposition temperature, it can undergo undesirable thermal decomposition. Ta having a dissociation temperature of about 1,100 ° C. ₂ O ₅ In this case, natural diamond particles can be used as a substrate without thermal damage, while synthetic diamond particles undergo undesirable thermal decomposition. Thus, metal oxides having a vaporization or dissociation temperature of at most 1,100 ° C. are preferred for use as reactants in carbon-thermal reduction processes for coating superabrasive particles. If tungsten oxide is used, a temperature of about 1,050 ° C. is preferred for either synthetic or natural diamond. It has been observed that coatings formed at such high temperatures result in reduced friability of the diamond as compared to unheated uncoated diamond.
[0031]
As the heating process continues, a layer of metal coating is deposited on diamond first as metal carbide and then as metal. The metal coats the exposed surface of the diamond at a rate that depends on the crystallographic orientation of the diamond surface. Advantageously, the method tends to produce a relatively uniform thickness of the coating on the superabrasive surface. Generally, the longer the exposure, the thicker the metal layer formed. Metal deposition is stopped by isolating the superabrasive from the coating forming powder when the desired coating thickness is achieved, or by removing the coating forming powder from a common inert atmosphere. Another method of stopping coating deposition is to pass an inert gas over the reacting particles at a high flow rate effective to reduce the temperature of the mixed particles and / or purge the atmosphere of reactive tungsten. is there.
[0032]
The inert atmosphere provides a medium for transporting chemical vapor species for performing the reduction and deposition steps. It is therefore important that the coating forming powder and the superabrasive to be coated are both in the same inert atmosphere. The inert atmosphere can be stationary, but some movement can move the species toward the solid material and tends to improve the coating speed. Therefore, it is preferable to pass an inert atmosphere over the solid feed bed. Flow may be stopped during the process. Excessive flow can dilute and carry away vaporous reactants before they reach the superabrasive surface. The concentration of reduction reaction by-products, such as carbon monoxide, can be increased in a static atmosphere or in a recycle atmosphere. This can slow down the metal coating process. Therefore, it is desirable to purge the by-product atmosphere during the process. This can be accomplished by evacuating a portion of the atmosphere and supplementing with fresh inert gas which supplements the evacuated capacity. Preferably, the volume of the inert gas atmosphere should be replaced about 5 to 20 times per hour.
[0033]
By the term "inert" is meant that the composition in an inert atmosphere is substantially free of oxygen or other substances that interfere with the reduction reaction. The absence of oxygen can be achieved by sweeping an inert gas or creating a vacuum over the superabrasive and the coating forming powder. The vacuum should be at a pressure effective to ensure that substantially all of the oxygen in the atmosphere is evacuated. Preferably, the vacuum should produce an atmosphere at an absolute pressure of less than about 3 Pa.
[0034]
Preferably, the inert atmosphere is generated by replacing the oxygen-containing atmosphere with an oxygen-free inert gas at ambient or higher pressure. The inert gas may pass over the solid reactant at a rate effective to move the vaporous reactant and promote efficient coating of the superabrasive. Representative inert gases suitable for use in the present invention are argon, helium, krypton, neon, nitrogen, xenon, and mixtures thereof. Argon and nitrogen are preferred.
[0035]
As mentioned above, the coating forming powder and the superabrasive particles do not require physical contact with each other to perform the new method. The particles and the powder may be isolated from each other. For example, the coating forming powder may be placed in a crucible and the superabrasive particles may be placed in the same inert atmosphere on a screen placed on the crucible. Preferably, the coating is performed batchwise by subjecting a solid batch of the coating forming powder and the superabrasive in the crucible to a heat treatment. Continuous processes are envisioned to be encompassed by the present invention. For example, the coating-forming powder and the superabrasive particles can be continuously placed in adjacent but distant bands parallel to the machine direction of a continuously moving belt conveyor. The belt may move through a furnace under an inert atmosphere. A specific embodiment of these individual particle processes is characterized in that the coated superabrasive product particles at the end of the method can be easily separated from the coating forming raw material particles. This is desirable where the coating forming particles and the superabrasive particles have approximately the same size. It also makes it possible to collect different sized product particles that can be damaged by mechanical operations such as sieving.
[0036]
A new method can be performed using a mixture of coating-forming powder and superabrasive particles. In a batch process, the mixture is placed as a batch in a single crucible and then heat treated.
[0037]
Preferably, the mixture is made by dry mixing the coating forming powder with the superabrasive. The mixture may be manufactured batchwise or continuously. Conventional compounding equipment such as ribbon mixers, drum tumblers and V-cone mixers can be used. A low energy blending device is preferred to avoid grinding the superabrasive particles. In another preferred embodiment, the coating-forming powder has a range of sizes different from the size range of the superabrasive particles. The particle size of the coating-forming powder is typically smaller than the superabrasive particles. Thus, the superabrasive particles can be easily separated from the coating-forming powder simply by sieving the mixture through an appropriately sized sieve. The method of separating the product particles from the mixture should preferably not employ elutriation. In this manner, the particles tend to abrasion the particles against each other and against an elutator ("elutriator") impact plate, thereby altering the particle size and / or damaging the metal-coated superabrasive product. . The superabrasive particles can be separated from the powder by adding the mixture to a liquid such as water. Here, the relatively low density powder floats and the relatively high density superabrasive sinks.
[0038]
In another preferred aspect, the coating-forming powder and the superabrasive should be arranged to expose a large surface area to an inert atmosphere. This can be achieved by placing those solid materials on a shallow stationary floor. Preferably, the bed depth should be up to about 20 times the average size of the particles in the bed. For granular or other irregularly shaped particles, the dimensions used to determine the average size of these particles are the nominal mesh size of the maximum / minimum size screen, which does not allow / pass all of those particles, respectively. Should be. When the coating forming powder is in a mixture with the superabrasive particles, the preferred bed depth should be up to 20 times the average particle size of the superabrasive. When the superabrasive is in sheet form, the dimension used to determine floor depth is the sheet thickness. Therefore, to coat a diamond film of about 1 mm thickness, it is preferable to place the coating forming powder on a floor up to about 20 mm deep.
[0039]
The container holding the powder and superabrasive particles that form the coating during the heat treatment should have a composition that is resistant to high temperatures and that does not interfere with the coating process. Preferably, a ceramic crucible may be used. Any refractory ceramic other than graphite ceramic, such as clay-graphite, is also suitable for use.
[0040]
The key parameters for controlling the new method are temperature and time. After the powder and the superabrasive forming the coating are assembled together in an inert atmosphere, the temperature is increased to initiate the reduction reaction. Generally, the critical temperature above the ambient temperature at which the reaction starts depends on the nature of the superabrasive and the metal compound. It is usually at least about 500 ° C. Usually, the method proceeds faster at higher temperatures, but the decomposition temperature of the superabrasive should not be exceeded. This is the temperature at which a superabrasive loses its superabrasive properties, i.e., superhardness, due to its form. Exposure of diamond to temperatures above about 1,200 ° C. at or below atmospheric pressure in an inert gas atmosphere rapidly converts the diamond to graphite. The preferred range is about 700-1,100 ° C. for optimal kinetics and minimal thermal damage.
[0041]
The elapsed time to achieve a complete metal coating depends on factors such as the size and type of the superabrasive strip, the flow rate of the inert gas, the heating rate and the reaction temperature. Heat treatment exposure at temperatures above about 500 ° C. in accordance with the present invention requires at least about 30 minutes, preferably at least about 1 hour, and most preferably 2 to 4 hours, to produce the desired results. Longer heat exposure times can be used. In general, a coating thickness of about 0.1 μm can be achieved per hour of heat treatment of diamond abrasive particles of a size of about 300-800 μm at a preferred temperature under an inert gas. As described herein, one of skill in the art should be able to identify, without undue experimentation, the appropriate combination of process conditions to achieve satisfactory results.
[0042]
In a typical implementation of the new method, the desired superabrasive to be coated, the coating metal and the coating forming compound are selected. The surface of the superabrasive piece to be coated should be free of metal contamination. Conventional methods of removing such contamination may be utilized. The superabrasive particles and the coating forming compound particles are placed in close proximity under an inert atmosphere, preferably an inert gas atmosphere. Preferably, these particles are mechanically blended together to form a mixture. Thereafter, the temperature is increased. The temperature is maintained at an elevated value below the decomposition temperature of the superabrasive for a time effective to produce a coating on the superabrasive particles. As the coating proceeds, inert gas may be provided across the feed and product beds at a flow rate effective to maintain the metal coating rate. When sufficient bond formation has occurred, the process is stopped and the superabrasive particles are cooled. The coated superabrasive is separated from the powder forming the excess coating. This results in a product in which the outer metal layer is chemically bonded to the superabrasive.
[0043]
The rate of cooling of the coated superabrasive particles to ambient temperature is not critical. Although it is recommended that thermal shock cooling of the product not damage the product, cooling from the reaction temperature to ambient temperature can take place in less than 1 hour, preferably less than about 30 minutes. When the temperature of the particle bed drops below about 150 ° C., the inert gas atmosphere can be removed, ie, an oxygen-containing gas can be introduced. The excess coating-forming powder can then be separated from the metal-coated superabrasive particles and recovered, sized and re-used in a subsequent coating procedure according to the invention. Thereafter, the coated superabrasive may be cleaned by exposure to hydrogen flowing over the outer metal surface at a temperature of about 600-800 ° C for at least about 30 minutes. Finally, the product is analyzed, inspected, and packaged for storage or transport.
[0044]
It has been found that replacing the inert gas with hydrogen for at least about 30 minutes as the particle bed temperature is decreasing during the cooling step may eliminate a subsequent separate oxide removal cleaning step. Preferably, the product is exposed to flowing hydrogen while the temperature is maintained in the range of about 700-800C. This hydrogen exposure during cooling not only cleans the metal surfaces of the coating particles, but also reduces some of the excess coating-forming powder to elemental metals or lower oxides, making them easier to remove from the product. Be separated. If too much metal compound is present, incomplete cleaning may result. If the in-situ cleaning process is incomplete, the metal-coated product will appear discolored. For example, tungsten oxide on a coated diamond can have a brown color. In such a case, a conventional re-hydrogen cleaning step may be utilized. That is, the product isolated from the powder forming the coating can be reheated in hydrogen.
[0045]
The metal-coated superabrasive particles produced according to the new method can be introduced into the polishing portion of a metal bond metal core polishing tool by various techniques well known in the art. For example, the particles can be combined with the particulate components of the metal binder composition, compressed under pressure ("cold compression") to form a shaped abrasive portion, and then sintered. The particles are also suitable for "hot compaction" with the simultaneous application of heat and pressure to form an abrasive portion. The particles can be used in so-called infiltration tool making methods. In this method, the coated superabrasive particles are filled into a powdery matrix of a metal binder component in a mold cavity, and then filled with a low melting infiltration metal or alloy whose gap has been melted. Additionally, the coated superabrasive is suitable for application to an abrasive tool by electroplating or brazing or possibly soldering (eg, with a single layer of abrasive grains on the surface of a metal tool body or core). .
[0046]
The use of coated superabrasives is useful for bonding diamond / metal binders, as well as cutting wheels, diamond saw blades and drill bits, single layer abrasive metal bond tools, grinding wheels, machining tools, dressing tools and coated wheels. Advantageously improves the life of the abrasives and tools of the abrasive tools and belts. In addition, the coated superabrasive has improved oxidation resistance that allows for the manufacture of certain abrasive tool components in the presence of oxygen without the need for an inert atmosphere.
[0047]
Certain advantages of the coated superabrasives of the present invention have been observed in brazing abrasive elements to a tool core or body. In the past, some tools have polished or cut the metal of the tool core or substrate (eg, shank, cylinder, wheel core or disk) under a non-oxidizing atmosphere to avoid thermal damage to the superabrasive. It had to be made by brazing the elements. The use of a non-oxidizing atmosphere is costly and increases the complexity of the manufacturing process. By applying a metal coating on the superabrasive surface, the brazing operation can be performed under atmospheric conditions, and higher temperature brazing materials can be used. Hotter brazing material may provide a more durable bond between the tool body and the abrasive or cutting element, and thus additional benefits may be realized over a longer tool life.
[0048]
Example
The invention will now be illustrated by way of an example of certain representative embodiments thereof. Here, in these examples, all parts, percentages and percentages are by weight unless otherwise indicated. All weight and scale units not initially obtained in SI units were converted to SI units. The particle size measurement of the granules uses the "x / y mesh" naming convention, where x and y are the sieve designation numbers of the US sieve series, x corresponds to the smallest network through which all of the particles pass, and y is This corresponds to the largest mesh through which none of the particles pass. That is, the 40/50 mesh diamond passes through the 420 μm mesh and is held by the 297 μm mesh.
[0049]
Example 1
50 g of 40/50 mesh De Beers brand SDA100 + synthetic diamond is combined with 75 g of -400 mesh (i.e., particles passing through a 37 [mu] m sieve) tungsten oxide (WO ₃ ) Placed in a ceramic crucible holding the particles. The diamond and tungsten oxide were manually stirred using a spatula to obtain a free-flowing homogeneous mixture. The crucible was placed in a Lindberg retort furnace and the furnace was evacuated continuously with nitrogen at 142 L / h (5 cubic feet per hour "CFH"). The furnace temperature was increased to 1,050 ° C. at approximately 10 ° C. per minute. When 250 ° C. was reached, argon was swept through the retort at the same rate instead of nitrogen. The diamond / tungsten oxide mixture was kept at 1,050 ° C. for 30 minutes in this argon atmosphere. The heating jacket was then separated from the retort and the furnace was cooled to 750 ° C. in about 10 minutes. At this temperature, hydrogen was swept through the retort at the same rate instead of argon. The heating jacket was returned near the retort furnace and the controller was set to maintain the furnace temperature at 750 ° C. under argon for 30 minutes. Thereafter, the heating jacket was again removed from the retort furnace and the furnace was cooled to room temperature over about 20 minutes. Hydrogen flow to the retort furnace was stopped when the temperature dropped to 100 ° C. The mixture was passed through a 100 mesh sieve to recover the diamond. Visual inspection showed that these diamonds had a matte gray surface color. Diamond pre-coated with tungsten, as confirmed by X-ray diffraction analysis, showed a similar color. Therefore, it was concluded that the diamond of this example was satisfactorily coated with tungsten metal. X-ray diffraction showed the presence of tungsten carbide in the metal layer, and Auger analysis confirmed the presence of carbon and tungsten in the coating.
[0050]
Example 2
The procedure of Example 1 was repeated except that 7.68 g of 30/40 mesh De Beers brand SDB1125 synthetic diamond was mixed with 11.52 g of tungsten oxide. After separating the diamond from the tungsten oxide, visual inspection showed that the surface of the coated diamond had a mottled brown / gray color. This surface characteristic is typical for tungsten coated diamonds where the tungsten is oxidized.
[0051]
These tungsten oxide coated diamonds were placed in a clean crucible and placed in a furnace. The furnace was swept with nitrogen as in the previous example and the temperature was raised to 750 ° C. When 250 ° C. was reached, the nitrogen was replaced by a hydrogen sweep at the same flow rate. The coated diamond was kept at 750 ° C. for 30 minutes in this hydrogen. Thereafter, the heating jacket was separated from the retort furnace, the furnace was cooled to room temperature, and the hydrogen flow was stopped. Visual inspection showed that the surface color of these coated diamonds was matte gray and that the tungsten coating on these diamonds was satisfactory. These coated diamonds weighed 7.92 g after coating and exhibited a total weight gain of 0.24 g.
[0052]
Example 3
The procedure of Example 1 was repeated except that 1.03 g of natural diamond was coated with 1.54 g of tungsten oxide. The operating conditions were also the same except that the furnace was heated to 1,000 ° C. to achieve the coating and held for 4 hours. Also, the hydrogen flow was stopped when the furnace was cooled to room temperature. After separation from the tungsten oxide particles, the coated diamond had a matte gray surface color and a total weight of 1.0414 g. Thus, these diamonds yielded a total of 0.3737 g of tungsten metal coating. Auger depth profile analysis of diamond previously coated in a similar manner suggests that the tungsten coating thickness was approximately 0.4 μm.
[0053]
Example 4
The procedure of Example 2 was repeated except that 40.117 g of 30/40 mesh natural diamond was coated with 60.176 g of tungsten oxide. After the second hydrogen heat treatment, the diamond had a matte gray surface color. This indicates that a satisfactory coating with tungsten was obtained.
[0054]
Example 5
Two samples of diamond film (Norton Company, Worcester, Mass.) Of 25.4 mm × 25.4 mm square and approximately 0.5 mm thick initially weighed 0.9428 g and 0.895 g, respectively. . Each film had one side with a rough textured and matte finish and a smooth glossy opposing side. The glossy side of each film sample was painted with a Microbraz® Green Stop-Off® type II paint (Wall Colmonoy Corp., Madison Heights, Mich.). This is believed to be a latex of suspended ceramic powder. The paint was dried, thereby masking the glossy side of the film. Each film was placed in a ceramic crucible, painted side down, on a 400 / mesh tungsten oxide floor weighing 1.5 times the initial diamond film weight. The rough side of these film samples was then coated with tungsten according to the procedure of Example 2.
[0055]
After the second hydrogen heat treatment, visual inspection showed that the diamond films had a dull gray color on the rough side. This indicates that a satisfactory tungsten coating was obtained. The masking material was gone on the shiny side of these films. A slight tungsten coating was evident near the edges, but no coating was found in the central area. After coating, the film samples weighed 0.9852 g and 0.9061 g. This represents a weight gain of 0.0154 g and 0.0111 g, respectively.
[0056]
Example 6
A bed of tungsten oxide particles was placed in a crucible and a steel screen was placed on the floor. Natural diamond was placed on the metal screen without contacting any of the tungsten oxide particles. The contents of the crucible were heated to 1,000 ° C. in argon, held for 4 hours, and otherwise treated as in Example 5. Finally, inspection of the product indicated that the diamond surface was partially coated with continuous pieces of shiny gray metal. The metal did not completely coat the diamond, but was sufficient to allow brazing to create a strong metal bond between the partially coated diamond and the metal substrate of the grinding tool. A large amount of surface was covered.
[0057]
Example 7
A total of 5.1569 g of 40/50 mesh De Beers brand SDB1125 diamond and 7.7354 g of -400 mesh tungsten oxide powder were placed in a ceramic crucible. These diamonds and tungsten oxide were mixed with a spatula to obtain a free flowing (free flowing) homogeneous mixture. The crucible was placed in a vacuum furnace (Oxy-Gon Industries, Inc., Epsom, NH) and the temperature controller was set to raise the furnace temperature to 1,050 ° C. The furnace was evacuated with a mechanical vacuum pump to an absolute pressure of about 3 Pa (0.03 mbar). The diamond / tungsten oxide mixture was held at 1,050 ° C. under vacuum for 60 minutes, after which the furnace temperature controller was set to cool the furnace temperature to room temperature (38 ° C.). The furnace was equipped with an internal shutter that introduced cooling air blown by an automatic cooling fan that reduced the temperature at about 10 ° C. per minute. The mixture was poured over a 100 mesh screen to separate the diamond from the tungsten oxide.
[0058]
These diamonds exhibited a purple color typical of a heavily oxidized tungsten coating. They were placed in a crucible to be cleaned, and the crucible was placed in a Lindberg retort furnace. The furnace was swept with hydrogen gas at 142 L / h and the temperature was raised to 750 ° C. These diamonds were kept at 750 ° C. for 30 minutes in a hydrogen atmosphere. The furnace temperature control was then turned off and the heating jacket was separated from the retort furnace. After the furnace temperature dropped to 100 ° C., the hydrogen gas flow was stopped. The diamond has a dull gray surface color, indicating the presence of a satisfactory unoxidized tungsten coating. Subsequently, these metal-coated diamonds were found to weigh 5.7206 g, corresponding to a weight increase of 0.5637 g.
[0059]
Example 8
To determine the effect of reaction temperature on the friability of diamond crystals and to determine if the coating method of the present invention produces the tough coated abrasive grains required for tool making, A survey was conducted.
[0060]
Diamond abrasive grains (American Boots Crushing, natural block diamond, 25/30 mesh size) were obtained from Cerac Inc., Milwaukee, Wisconsin. WO supplied by ₃ Mix with powder (5 g diamond and 7.5 g WO ₃ ) And heated at the temperatures and times listed below. The reaction was performed as described in Example 4, except for the variables listed in the table below.
[0061]
After separating the coated grains from the remaining tungsten oxide powder, the friability of the diamond grains is measured using a standard (FEPA Standard) for measuring the relative strength of a diamond grit for sawing in FEPA (Federation European Des Fabricants De Products Abrasifs). for Measuring the Relative Strength of Saw Daimond Grits, 1st edition, May 30, 1994).
[0062]
Modifications to the FEPA diamond friability test standard include (1) using grade 25 52100 steel ball bearings as test balls, (2) weighing diamond samples to 0.4000 ± 0.0005 g, (3) Substituting the sieve size (especially the upper control sieve size 915 by 920, the 645 by 650 μm, the lower control sieve size by 605, 505 by 509, and 425 by 429, and the breaking sieve size) (600 replaced by 605, 505 replaced by 509 and 425 replaced by 429 μm), (4) using a vibrating sieve instead of a sieve shaker, and (5) the result reaches the half-life of diamond grains Should be recorded and reported as the number of cycles required for The PA standard used the time required to destroy half of the diamond). The friability results and visual observations of diamond coating properties are listed in the table below.
[0063]
[Table 2]

[0064]
These data show that the particles coated with tungsten at a temperature of 1,050 ° C. (sample 6) compared to the particles coated with tungsten at a temperature of 800 or 850 ° C. (samples 2-4). Exhibit an unexpected increase in the toughness of diamond abrasive grains (ie, relatively small friability). The improvement was also observed compared to the uncoated granules (Samples 1 and 5). Under the process conditions chosen for this experiment, the coating was continuous when the reaction was performed at a relatively high temperature and intermittent when the reaction was performed at a relatively low temperature. . These results suggest the benefits of continuous coating. Because the coefficient of thermal expansion of tungsten is about 49% greater than the coefficient of thermal expansion of diamond, the improved toughness of the coated diamond results from the shrinkage of the continuous tungsten coating during cooling, thereby placing the diamond in compression. Can be done.
[0065]
The specific forms of the invention have been selected for description, and the above description has been prepared in specific terms for the purpose of sufficiently and extensively describing these forms of the invention to those skilled in the art. However, it should be understood that various substitutions and modifications that result in substantially equivalent or superior results and / or performance are deemed to be within the scope and spirit of the claims.

Claims (28)

(A) heating a coating-forming powder containing a superabrasive and a metal compound that can be thermally reduced by the superabrasive to a temperature higher than ambient temperature in an inert atmosphere
(B) maintaining the material and superabrasive at a temperature above the ambient temperature for a time effective to reduce the metal, thereby chemically bonding to at least a portion of the surface of the superabrasive; Forming a metallized superabrasive having a patterned metal layer; and (c) separating the coating-forming powder from the metallized superabrasive.
A method of coating a superabrasive with a metal, comprising: (A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound;
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) bringing the superabrasive and the coating-forming powder to a reaction temperature of at least about 500 ° C. and less than the decomposition temperature of the superabrasive, and applying a layer of metal to at least a portion of the surface of the superabrasive particles. Exposing for a time effective to deposit and chemically bond;
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
A metal coating method. A plurality of superabrasive particles ranging in size from about 0.1 μm to a maximum of about 5 mm, with a total amount greater than a stoichiometric amount effective to produce a predetermined thickness of a metal coating on the superabrasive particles of at least about 100 nm. The metal coating method according to claim 2, comprising placing together with a coating forming powder containing the metal. 4. The metal coating method of claim 3, wherein the size of the superabrasive particles is in the range of about 300-600 [mu] m and the weight of the coating-forming powder present is about 1.5 times the weight of the superabrasive particles. . 3. The metal coating method according to claim 2, wherein the metal layer bonded to the surface of the superabrasive is a continuous layer. 3. The metal coating method of claim 2, wherein the exposing step is performed such that the mixture is present on a stationary bed having a depth of up to about 20 times the average superabrasive particle size. 3. The metal coating method according to claim 2, wherein the inert atmosphere includes a vacuum at an absolute pressure of less than about 3 Pa. 3. The metal coating method according to claim 2, wherein the inert atmosphere comprises an inert gas selected from the group consisting of nitrogen, helium, neon, argon, krypton, xenon and mixtures thereof. 3. The metal coating method of claim 2, wherein the superabrasive particles are sheets of diamond having characteristic dimensions greater than about 5 mm. 10. The metal coating method of claim 9, wherein the superabrasive particles comprise a diamond film made by chemical vapor deposition. 10. The metal coating method of claim 9, further comprising masking at least a portion of the surface of the superabrasive particles with a barrier material prior to the exposing step. The metal coating method according to claim 9, wherein the at least one superabrasive particle is a flat diamond sheet having a thickness of less than about 1 mm. Prior to separating the product fraction and the by-product fraction, replacing the inert atmosphere with hydrogen gas, and at least about 700-800 ° C. in the hydrogen gas atmosphere to an oxide removal temperature. 3. The metal coating method of claim 2, further comprising maintaining the superabrasive particles for 30 minutes. 3. The metal coating method according to claim 2, wherein the superabrasive particles and the coating forming powder are exposed to a reaction temperature in the absence of a reducing agent other than the superabrasive. The method of coating a superabrasive according to claim 1, wherein the coating forming powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum and combinations thereof. 3. The metal coating method according to claim 2, wherein the coating forming powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum and combinations thereof. (A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound, and the compound is tungsten, vanadium, tantalum; And oxides of molybdenum and combinations thereof,
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) bringing the superabrasive and the coating-forming powder to a reaction temperature at least in the range of about 500 ° C. to less than the decomposition temperature of the superabrasive with a continuous layer of metal on at least a portion of the surface of the superabrasive particles; Exposing for a period of time effective to deposit and chemically bond
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
Metal-coated superabrasive particles produced by a method comprising: (I) providing a metal core;
(II) metal-coated superabrasive particles,
(A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound;
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) bringing the superabrasive and the coating-forming powder to a reaction temperature at least in the range of about 500 ° C. to less than the decomposition temperature of the superabrasive with a continuous layer of metal on at least a portion of the surface of the superabrasive particles; Exposing for a period of time effective to deposit and chemically bond
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
Providing metal-coated superabrasive particles produced by
(III) brazing the metal-coated superabrasive particles to the metal core;
A method for producing a polishing tool, comprising: 19. The method of claim 18, wherein the coating forming powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum and molybdenum and combinations thereof. An abrasive tool having a metal core formed by bonding metal-coated superabrasive particles in a powdered metal matrix composite and adhering the composite to the core.
(A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound;
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) bringing the superabrasive and the coating-forming powder to a reaction temperature at least in the range of about 500 ° C. to less than the decomposition temperature of the superabrasive with a continuous layer of metal on at least a portion of the surface of the superabrasive particles; Exposing for a period of time effective to deposit and chemically bond
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
A polishing tool having a metal core, wherein the metal-coated superabrasive particles are produced by a method comprising: 21. The polishing tool of claim 20, wherein the coating-forming powder is selected from the group consisting of oxides of tungsten, vanadium, tantalum, and molybdenum, and combinations thereof. 21. The metal-coated superabrasive particle is an at least partially metal-coated diamond film, the film being brazed to a metal core at a temperature of about 850 to 1,100C. A polishing tool according to item 1. A metallized article comprising a structural diamond part coated with metal,
(A) heating the coating-forming powder containing the diamond and the metal oxide to a temperature higher than ambient temperature in an inert atmosphere;
(B) maintaining the powder and the diamond at a temperature above the ambient temperature for a time effective to reduce the oxide, thereby chemically bonding to at least a portion of the surface of the diamond. Making a metallized article having a metal layer; and (c) separating the powder from the metallized article.
A metallized article comprising a structural diamond part coated with a metal by the method comprising: 24. The metallized article of claim 23, wherein said coating forming powder is selected from the group consisting of tungsten, vanadium, tantalum and molybdenum and combinations thereof. (A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound;
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) depositing the superabrasive and the coating-forming powder at a reaction temperature in the range of at least about 700 ° C. to about 1,075 ° C. with a continuous layer of metal on at least a portion of the surface of the superabrasive particles; Exposing for a period of time effective to bind and chemically bond;
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
Metal-coated superabrasive particles produced by the method comprising: 26. The metal-coated superabrasive particles of claim 25, wherein the coating-forming powder is an oxide of a metal selected from the group consisting of tungsten, vanadium, tantalum, and molybdenum and combinations thereof. An abrasive tool having a metal core formed by bonding metal-coated superabrasive particles in a powdered metal matrix composite and adhering the composite to a metal core, wherein the metal-coated superabrasive particles have a metal core formed by adhering the composite to a metal core. Super abrasive particles
(A) providing at least one superabrasive particle and a powder of a coating-forming metal-containing compound, wherein the metal is thermally reducible from the compound;
(B) placing the superabrasive particles and the coating forming powder together in an inert atmosphere;
(C) depositing the superabrasive and the coating-forming powder at a reaction temperature in the range of at least about 700 ° C. to about 1,075 ° C. with a continuous layer of metal on at least a portion of the surface of the superabrasive particles; Exposing for a period of time effective to bind and chemically bond;
(D) cooling the superabrasive particles and the coating-forming powder to a temperature below the reaction temperature; and (e) separating the mixture to provide a metal-coated substantially free of the coating-forming powder. Obtaining a product fraction of superabrasive particles, and a by-product fraction of a coating-forming powder substantially free of metal-coated superabrasive particles;
A polishing tool having a metal core, produced by a method comprising: 28. The polishing tool of claim 27, wherein the coating forming powder is an oxide selected from the group consisting of tungsten, vanadium, tantalum, and molybdenum and combinations thereof.